1. Field of the Invention
The present invention relates to a rollover detection device for a general-purpose engine for detecting a rollover of a driving unit such as a rammer that is driven by a general-purpose engine.
2. Description of the Related Art
A rolling compaction machine for use in compacting a paved surface or ground surface is called a “rammer.” As described in Japanese Utility Model Registration No. 3122696, a general-purpose engine is used for driving a rolling compaction plate, or a rammer member, wherein the rammer member serves as a member to be driven by the general-purpose engine. The general-purpose engine mounted in a driving unit such as a rammer has a crankcase in which a crankshaft is installed rotatably, and a cylinder in which a piston connected to the crankshaft by a piston rod is incorporated so as to be able to reciprocate axially. A bottom part of the crankcase is provided with an oil pan to store lubricating oil. The lubricating oil is supplied to a lubrication section, which is a sliding section such as a bearing that supports the crankshaft rotatably. The crankcase is provided with an oil pump for supplying the lubricating oil to the sliding section, and the oil pump is driven by the crankshaft.
As described in Japanese Unexamined Patent Application Publication Nos. 1992-241713 and 1997-49414, a strainer is incorporated in a tip end of a lubricating oil feed pipe for guiding the lubricating oil to the oil pump. The lubricating oil within the oil pan is drawn through the strainer, functioning as a drawing port, into the lubricating oil feed pipe and then supplied to the sliding section.
Japanese Patent No. 2713765, on the other hand, describes an engine stop device that is provided with a detection switch for detecting the amount of lubricating oil stored in an oil pan of a general-purpose engine, and stops the engine when the amount of lubricating oil drops to a certain level or lower.
The driving unit such as a rammer is tilted when used, depending on the conditions in which the driving unit is used. When the driving unit is tilted, naturally the general-purpose engine mounted in such a driving unit is also tilted. Even when the driving unit is tilted under normal use, the lubricating oil within the oil pan can be supplied to the oil pump and hence to the sliding section. However, if the driving unit rolls over, even when the engine is driven while having a predetermined amount of lubricating oil stored in the oil pan, the lubricating oil cannot be suctioned into the lubricating oil feed pipe.
With regard to rollover directions in which the driving unit such as a rammer can roll over, there are two, front and rear, rollover directions where the front surface side or the rear surface side of the engine is tilted downward, and there are two, left and right, rollover directions where the left-side surface or the right-side surface of the engine is tilted downward. The driving unit sometimes rolls over in multiple directions, such as to the front and to the right. When the driving unit rolls over in such a manner, the lubricating oil cannot be guided to the oil pump or supplied to the sliding section. Subsequently, the lubricating oil enters the inside of the piston or other parts that require no lubrication. In this case, the engine needs to be stopped. Examples of the conditions where the driving unit rolls over include not only when the front surface side or the rear surface side of the engine is tilted completely downward, but also when the driving unit tilts to the extent that the engine needs to be stopped.
Although detection of a rollover of the engine was attempted by attaching a rollover sensor to the driving unit, it is inevitable for the rollover sensor to erroneously detect a rollover of the driving unit such as a rammer, which vibrates. Thus, a rollover could not be detected accurately.
Because the lubricating oil within the oil pan is not guided to the lubricating oil feed pipe when the driving unit rolls over, a pressure sensor is provided at a discharge port of the oil pump to detect that the lubricating oil is not discharged from the oil pump and thereby detect a rollover of the driving unit.
However, it is necessary to take into consideration that the driving unit rolls over in all of front-rear and left-right directions described above. In a general-purpose engine in which the oil pump is incorporated in an end wall part of the crankcase and the strainer is incorporated within the end wall part, the pressure sensor cannot detect a rollover in a certain direction. In other words, when the driving unit rolls over in such a direction where an opening part of the strainer is tilted upward, the lubricating oil is stopped from being guided from the opening part of the strainer to the lubricating oil feed pipe, and consequently the pressure of the lubricating oil in the discharge port of the oil pump can be detected to determine the rollover of the driving unit. On the other hand, when the driving unit rolls over in such a direction where the opening of the strainer is tilted downward, the lubricating oil is guided from the opening part to the lubricating oil feed pipe, and, as a result, the rollover of the driving unit cannot be detected.